It has been established that alkylpyrazines are natural components of tobacco smoke, and are contributors to tobacco smoke flavor [A. Baggett et al J. Chromatog, 97, 79 (1974)]. Further, it has been disclosed in the patent literature that addition of alkyl pyrazines to tobacco results in an improvement in the flavor of smoking compositions as perceived by a test panel.
U.S. Pat. No. 3,402,051 describes a process for imparting a popcorn-like flavor and aroma to tobacco and foodstuffs by the incorporation of a 2-acetylpyrazine derivative therein.
Other patents which disclose the addition of various pyrazine compounds to tobacco and foodstuffs as a means of providing flavor or flavor enhancement include U.S. Pat. Nos. 3,684,809; 3,705,158; 3,754,934; 3,764,349; 3,767,426; and 3,881,025.
U.S. Pat. No. 3,914,227 discloses pyridyl and pyrazyl ketones and their use in altering the organoleptic properties of tobacco and foodstuffs, and U.S. Pat. No. 4,166,869 discloses acylpyrimidines useful as flavorants for the same type of applications.
Alkylpyridines have also been found to be useful tobacco additives. As an example, U.S. Pat. No. 3,625,224 describes the use of methylpyridines, ethylpyridines and various dialkylpyridines as tobacco additives. U.S. Pat. No. 3,381,691 discloses 2-methyl-5-isopropylpyridine as a tobacco additive.
It is characteristic of pyridine, pyrazine, pyrimidine and other heterocyclic derivatives employed as tobacco flavorants in the prior art, as illustrated by the above described technical literature, that the respective heterocyclic derivatives have the disadvantage of both high volatility and low odor threshold. Both of these properties significantly restrict the extent that these heterocyclic derivatives can be utilized as flavorants in tobacco compositions. A quantity of a pyrazine or pyridine derivative in a tobacco composition sufficient to have a noticeable effect in low delivery cigarettes causes a marked pack aroma.
U.S. Pat. No. 4,036,237 endeavors to overcome some of the disadvantages of the above-described flavorant technology. The said patent provides for the incorporation in smoking compositions of a flavorant compound which imparts cherry-like or fruity flavor to the smoke thereof, which flavorant compound is not lost during the manufacture and storage of the flavored smoking composition, and which is readily released when the smoking composition is burned. Illustrative of a U.S. Pat. No. 4,036,237 flavorant compound is ethyl 2,2-dimethyl-3-hydroxy-3phenylpropionate.
U.S. Pat. No. 4,259,969 describes smoking flavorant-release additives such as 2,3-dihydroxy-2,3-dimethyl-1,4-bis(3,5,6-trimethyl-2 pyrazinyl)butane. Under smoking conditions there are released substituted-pyrazine pyrolysis products which enhance the flavor of the mainstream smoke and improve the aroma of the sidestream smoke.
U.S. Pat. No. 4,312,368 and related U.S. Pat. No. 4,479,003 describe heterocyclic-hydroxy-substituted alkanoate flavorant additives such as ethyl 2-(2-butyl)-3-hydroxy-3-methyl-3-(3-pyridyl)propionate: ##STR2## Under normal smoking conditions the favorant additive pyrolyzes into components which contribute enhanced flavor and aroma to the smoke streams.
U.S. Pat. No. 4,171,214 is of general interest as disclosing pyrazine intermediates which are related structurally to the present invention smoking composition additives.
There is continuing research effort to develop improved smoking compositions which contain a new and efficient low volatility flavorant-release additive, and which generate mainstream smoke with flavorant-enhanced taste and character under smoking conditions.
Accordingly, it is an object of this invention to provide smoking compositions having incorporated therein a flavorant component which is characterized by lack of mobility and/or volatility at ambient temperature.
It is another object of this invention to provide smoking compositions having incorporated therein a flavorant-release additive which under normal smoking conditions yields pyrolysis constituents which impart improved flavorant properties to mainstream and sidestream smoke.
It is a further object of this invention to provide novel heteroaromatic compounds of low volatility which are adapted to be incorporated into cigarette fillers, and which under normal smoking conditions release volatile alkylpyrazine and other flavorant constituents into cigarette smoke.
Other objects and advantages of the present invention shall become apparent from the following description and examples.